GMC Hummer H3 2008 Owner's Handbook Manual page 239

Starting and Operating Instructions
• Don't tow a trailer at all during
the first 800 km (500 miles)
your new vehicle is driven. The
engine, axle or other parts
could be damaged.
• During the first 800 km (500
miles) of trailer towing, don't
drive over 80 km/h (50 mph)
and don't make full-throttle
starts.
• Be sure your vehicle's tyres are
inflated to the limit for cold
tyres.
See the tyre information label
for your vehicle's tyre inflation
specifications.
Also, see "Vehicle Loading"
earlier in this section for more
information.
. . . 238
• Never exceed the Gross Trailer
Weight Rating.
• Trailer tongue weight must be
included in the total vehicle
weight.
Trailer tongue weight should
never exceed 272 kg (600 lbs).
• When towing a trailer with an
automatic transmission, oper-
ate your vehicle in D (Drive).
You may want to shift into 3
(Third) or, if necessary, a lower
gear if the transmission shifts
too often.
When towing a trailer with a
manual transmission, it is best
not to use the highest gear.
• You should not park vehicles
with trailers on a grade (hill).
However, if you must park on a
grade, have someone place
wheel chocks under the trailer
wheels.
For more information, see
"Parking On Hills" later in this
section.